Урок №4. Мускулатура человека. Muscular system

Vocabulary:

muscular tissue – мышечная ткань voluntary muscles – произвольно скоращающиеся мышцы involuntary muscles – непроизвольноскоращающиеся мышцы

Movements – движения contractile tissue – сокращающаяся ткань skeletal muscles – скелетные мышцы Cardiac muscle – сердечная мышца smooth muscles – гладкие мышцы Contraction – сокращение

Muscular system is the system of Human Body that provides motor power for all movements of body parts. Muscular system is composed of special tissue called muscular tissue. Muscles have the ability to contract actively to provide the force for movements of body parts. Muscular system is an important system of human body because without it, life will completely stop. Muscles produce not only those movements that are under the control of our will and that we can see and feel, but also those movements that are responsible for activities like breathing, digestion of food, pumping of blood etc. Their function is to produce force and cause motion.

Functionally we divide all muscles into two groups: voluntary and involuntary muscles.

Muscle is a contractile tissue (сокращающаяся ткань) and is derived from the mesodermal layer (мезодермальный слой) of embryonic cells. Muscle cells contain contractile filaments (нити) that move past each other and change the size of the cell.

There are three types of muscle tissue. They are classified as skeletal, cardiac, or smooth (гладкие) muscles.

S keletal muscle or "voluntary muscle" (произвольно сокращающаяся мышца) form most of the human body weight. They are under the control of human will and all body movements occurring by our will are produced by skeletal muscles. They are called skeletal muscles because they are almost always found attached to the skeleton and produce movements in different parts of the skeleton. An average adult male is made up of 42% of skeletal muscle and an average adult female is made up of 36%.

Smooth muscle or "involuntary muscle" form the soft body organs like stomach, intestine, blood vessels uterus, urethra, bladder etc. They are not under the will of human beings and are responsible for unconscious body activities like digestion of food. They are called smooth muscles because when seen under the microscope, they do not have any striation in contrast to the other two types of muscles.

C ardiac muscle is also an "involuntary muscle" and is found only in the human heart. They are extremely strong and powerful muscles. They are not under the control of human will. The pumping of blood by human heart is because of the force provided by the contraction of cardiac muscles.

1. Answer the questions.

1. Give the definition of the word ‘muscle’.

2. What do muscle cells contain?

3. How are they classified?

4. What is a skeletal muscle?

5. What is a smooth muscle?

6. What is a cardiac muscle?

Muscular system has the following important functions in human body;

1. MOVEMENTS OF BODY PARTS: Skeletal muscles are responsible for all voluntary movements of human body parts. They provide the force by contracting actively. In other words, muscles are motors of body where chemical energy of food is converted into mechanical work.

2. STABILITY AND POSTURE: Skeletal muscles stabilize human skeleton and give a proper posture to human beings. Some joints of human body are weak and they require the support of muscular system to achieve stability. Skeletal muscles are very important for such joints.

3. HEAT PRODUCTION: A large share of body’s energy is used by muscular system. As a result of high metabolic rate, muscles produce great amount of heat in the body. Heat produced by muscles is very important in cold climates.

4. CIRCULATION: Cardiac muscles provide the main force for circulation of blood throughout human body. The regular pumping of heat keeps the blood in motion and nutrients are readily available to every tissue of human body.

5. HELP IN DIGESTION: Smooth muscles of organs like stomach and intestine help the digestive system in the process of digestion of food.

How a Muscle Works

A skeletal muscle works by CONTRACTING (getting shorter).

The muscle can shorten as much as 1/3 its resting length.

Each muscle cell is made up of many smaller MYOFIBRILS

The MYOFIBRILS are in contact with a nerve ending.

The nerve releases a chemical called a NEUROTRANSMITTER.

The Neurotransmitter stimulates the entire muscle cell to contract.

Muscles work in pairs. The biceps muscle will bend the arm at the elbow and the triceps muscle will straighten the arm. While one muscle in the pair contracts the other must relax.

VIDEO TASKS:

1. Give the four properties possessed by muscle tissue. 2. Differentiate between skeletal, smooth and cardiac muscle. 3. Describe how muscles work together to create movement. 4. Discuss the ways in which skeletal muscle fiber cells differ from other cells in the body. 5. Describe the effects of strenuous exercise on the muscular system. 6. Tell how the terms "voluntary and "involuntary relate to muscular tissue.